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*To*: "Peter M. Saama" <saama@pilot.msu.edu>*Subject*: Re: Interpretation of Components for Splines*From*: "B. Cullis" <cullisb@wagsun.agric.nsw.gov.au>*Date*: Fri, 30 Apr 1999 08:00:41 +1000 (EST)*cc*: asreml@ram.chiswick.anprod.csiro.au*In-Reply-To*: <4.1.19990429102819.00ae2230@gogreen.ans.msu.edu>*Sender*: asreml-owner@ram.chiswick.anprod.csiro.au

On Thu, 29 Apr 1999, Peter M. Saama wrote: > Hello: Dear Peter, > > When we fit spl(t), and dev(day) in ASREML, the .asr file contains output > that looks like this: > > Source Model terms Gamma Component > Compnt/StndErr > spl(time) 18 18 6.65133 > 4.113614 1.41 P > dev(time) 20 20 0.603323E-01 > 0.103056E-02 0.47 P > ... > > In the above table is 4.113614 a smoothing parameter or is it a variance > component? Furthermore, in the above table, is 0.103056E-02 a parameter > used in specification of the roughness penalty or is it a variance component? The component for spl(time) is a variance component, but it controls the amount of smoothing. If this component (actually the ratio gamma) tends to zero, the spline fit tends to a straight line, as it gets large the fit tends to interpolation. The additional variance component, ie dev(time), allows for the presence of group effects, and can only be fitted if there is replication at each (or most) time point. This is in line with the usual one-way random effects analysis where you would fit y~ mu !r group in asreml to get correct analysis ie estimating both an error and between groups variance. The usual roughness penalty that is described in most smoothing texts is actually lambda = 1/gamma(spl). I hope this helps best wishes > > Respectfully, > > Peter M. Saama / > -- > Asreml mailinglist archive: http://www.chiswick.anprod.csiro.au/lists/asreml > ............................................................................... Brian Cullis Tel: 02 6938 1855 NSW Agriculture Fax: 02 6938 1809 Wagga Agricultural Institute email: brian.cullis@agric.nsw.gov.au Pine Gully Rd WAGGA WAGGA NSW 2650 -- Asreml mailinglist archive: http://www.chiswick.anprod.csiro.au/lists/asreml

**Follow-Ups**:**Re: Interpretation of Components for Splines***From:*"Peter M. Saama" <saama@pilot.msu.edu>

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